Whilst the lesser enthusiast might be looking for flatter courses, you want to set off for the toughest marathons. Here are your options:

Grandfather Mountain Marathon, Boone, N.C.

You begin running at the height of 3,300 feet and finish it at the height of 4,200 feet at North Carolina's Grandfather Mountain Marathon. The journey through Sugar Mountain and Ski Beech ski resorts is for the keeps. Annually, around 400 racers take part in the event.

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Big Sur International Marathon, Carmel, Calif

The place is endowed with breathtaking beauty and some biggest challenges. The Hurricane Point needs the racer to climb a height of 300 feet for just one mile. The sight of Northern California hills is what draws the racers to this place the most.

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Equinox Trail Marathon, Fairbanks, Alaska

Racing up the Alaska's Equinox Marathon is one hell of a challenge. The trail is harsh and hilly and the weather is as unpredictable as unpredictable can get. You may be having a sunny day at 27 degree Celsius and the next thing you know that snow has stacked up will 7 inches.

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Lake Tahoe Marathon, Tahoe City, Calif.

You would be gasping – both by the beauty surrounding you and the task up ahead. There are few places on earth as beguilingly beautiful as the Lake Tahoe and its environs. And thus, it gives the runners options aplenty owing to its diversified landscapes. The final race, after two races of 26 miles each, is as long as 72 miles and does demand a lot of endurance.

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Great Wall Marathon, Tianjin Province, China

You are in for a mind-boggling marathon climbing up the Great Wall of China. It is a momentous place to be and you can always tell your great grandchildren about how you climbed the Great Wall of China. It takes on an average of 6 hours for runners to finish the race.

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Antarctic Ice Marathon, Union Glacier Camp, Antarctica

And then there is that. This is one adventure to be grabbed by both hands. Running at a place with the most extreme climate makes for one herculean marathon. You have to endure winds at 30 mph and run on ice for more than 26 miles.

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Inca Trail Marathon, Cusco, Peru

This takes the top spot when it comes to the toughest marathon. Running along the stones and over them for 27 miles is taxing, but this Sacred Valley town would never let you complain. You will be crossing the town of Machu Picchu and that is worth every gram of energy spent

For dedicated runners, the tougher the marathon is, more gratifying they feel after crossing the finish line.